Concentrator



FIG. 1 is a front perspective view of a concentrator showing our design;

FIG. 2 is a rear perspective view thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a left side elevational view thereof;

FIG. 6 is a right side elevational view thereof;

FIG. 7 is a top plan view thereof; and,

FIG. 8 is a bottom plan view thereof.

The broken lines showing portions of the concentrator designs in FIGS. 1-8 show unclaimed subject matter only and form no part of the claimed design. 

The ornamental design for a concentrator, as shown and described. 